PERCEPTION, in logic, the first and most simple
act of the mind, whereby it perceives, or is conscious
of its ideas. See LOGIC, Part I. and METAPHYSICS,
no 36—39. 77.
PERCEPTIVE faculty of the human mind.—Con-
cerning this there have been very great controversies.
Every one knows that there are sensations arising in
our minds; but the question is what it is that per-
ceives them, whether it is a man as a compound being
of soul and body, or whether the living percipient is
not a mind, or spirit alone, without a body, or else a
quality only, resulting from the construction of a body
without any distinct or separate spirit annexed thereto.
These are difficulties probably never to be demon-
strated, and we must at last be content with a probable
proof only.
Man is so wonderfully made, that he seems to assign
a place to every one of his sensations, and yet reason
and experience tell him, that in truth they cannot ex-
ist, or be, where he is apt too hastily to judge, or
suppose them to be; for as nothing can act where it
is not, so the perceptive power of man cannot possibly
perceive any thing without or beyond himself. It is
generally agreed, that the secondary qualities of body
(as they are called) do not exist external to the man,
but only the primary ones; though Dr Berkeley at-
tempted to shew that they both exist together, and
that where-ever the colour was, there likewise was the
extension. If this could be satisfactorily made to ap-
pear, the doctor's system would stand good for the
non-existence of every thing but spirit and ideas; but
it cannot, and to confine the argument to one sense
alone, to wit, sight; that man perceives colour we
are sure of, and therefore it must be within him, or he
would act where he was not. Now if he perceived
extension, that must likewise be within him too, but
then he could perceive no extension larger than him-
self:—but as neither extension nor colour have any
place assigned them in the body, surely it is not the
body, or any conformation thereof, that perceives.
We may then suppose that it is something else, which
is joined with the body that is the percipient, which
let us name mind or soul; this mind should seem to
be one simple uncomposed being, otherwise it could
not be conscious that successive perceptions were the
affections of the same thing.
Colour, though hastily judged to be without the
mind, Berkeley and Malbranche have sufficiently shew-
ed not to be so; and that extension is so, seems also
true; because it perceives none of its sensations ex-
tended, but only assigns or fixes a place for them, these
of colour in particular, external to the man, although
in fact they may not be without him; and this place
is only determined by an operation of the mind, sug-
gesting or supposing distance, from an experimental
obstruction to the motion of some members of the
body by which the touch is affected as well as the sight,
and so both the tangible and visible object concluded,
though too precipitately, to be in one and the same
place where the obstruction is likewise judged to be,
and hence it obtained the supposition or suggestion of
distance; and as we have no sensations to which we
do not ascribe some distance or place, there must be
place or space existing, or it could not be supposed.
And therefore as nothing is perceived or suggested
but what is supposed in some place, so nothing can
exist but what constitutes space, or is in it, and must
have some extension.
But then the mind of man surely cannot be extend-
ed beyond his body, though it often supposes an ex-
tension far beyond; and if the extension imagined
was in the mind, and not a mere operation thereof,
by way of supposition, it could not guess so much
amiss about the extension of objects which has not
been familiar to the other organs of sense, as we of-
ten find it does; for it seems to be a vulgar error to
entertain a notion of the mind's judging of any dis-
tance or magnitudes from any pictures conjectured to
be in the fund of the eye, or in itself: in the former
case, if there be any picture in the bottom of the eye,
it would judge every object in an inverse position to
the body, which is contrary to experience; neither
does the mind judge of any magnitude according to
any such pictures, but of the real external magni-
tudes; and seldom errs much, unless the objects be
very remote.—If the bulk of objects were judged of
by the pictures in the eye, a flea or mite must judge
every object very small to what a man does, because
the picture will be diminished nearly as the eye is
less: indeed these insects may see distinctly smaller
things than man, because the objects may be brought
nearer their small eyes, without throwing the focus of
the rays beyond the retina, as the same distance of
object would do in a larger eye, and prevent distinct
vision; and it is highly probable, that these small in-
sects cannot see objects at a great distance, unless they
are much larger than what a man can see at the like
distance; but then what they do see they judge to be
of the same bigness that a man does; and so must
every creature, let its eyes be of what dimension or
number you please. It is a vague notion opticians
have, who imagine that one, like a microscope lens,
will magnify the picture on the retina, whereas just
the contrary takes place; for when the eye is used
alone, without such a lens, the shorter focus of the
eye forms the picture, and the longer is at the ob-
ject; but when a lens is used by way of a microscope,
the object is in the shorter, and the picture at the
longer focus, just contrary to the method of common
vision.
So, again, if the mind was conscious of a picture
in the eye, it would perceive as many objects the crea-
ture had eyes; whereas it judges of no more, let the
number of eyes be as they will, than it does by the
help of any other of the senses.
From all which we may conclude, that figure, ex-
tension, and motion, are not perceptible objects; but
that sensations alone are such, the former being only
imagined, by an operation of the mind, to exist ex-
ternal to it; and that if they did not so exist, the
mind could not imagine any extension, figure, and
motion; for there never is found any of them percei-
vable by it, nor any figure or motion attending a
simple sensation. Indeed it is too commonly thought,
that there is a shape perceived with colour, or a coloured shape; but no object appears of one simple colour to a fixed eye, but every part of the object exhibits a different degree of colour; and these degrees separate sensations, to which the mind ascribes a place, though, in fact, the colour is not in the place so judged of, but something else that gives resistance to the actions of the mind on the body; and from hence it supposes there must be something existing there which gives rise to the colour perceived by it.—It is impossible the mind should perceive the images of things within itself, unless it was equally extended with the things themselves; and if not, how can it be thought that an ideal world can exist within the mind, as some philosophers have conjectured? Surely it cannot be; but it must be only imagination that directs us to the external existence of real things. We cannot properly be said to imagine what does not or has not really existed; for let a blind man try if he can imagine colour, or a deaf man sound, and he will find himself at a loss. Father Malbranche indeed tells us, that a man may have an idea of a golden mountain that never existed; and a man may recollect the figure of a mountain which he has formerly imagined, and remember the colour of gold which he lately had a perception of, and suppose it possible they may be connected, and call this operation of his mind an idea if he pleases; but, after all his efforts, if he should happen to think of a mountain as large as Shooter's hill, he will hardly allow it to be contained in his mind.